The present invention relates to a method of manufacturing one and two piece alloy wheels for vehicle tires. Alloy vehicle wheels and in particular aluminum alloy wheels are quite popular due to their aesthetic appearance and light weight. Because aluminum alloys are not readily susceptible to welding due to the deleterious effect of the welding process on the strength of the metal, it has been standard practice to manufacture separately the disc or wheel center and the inner and outer rims and subsequently to assemble the component parts by a suitable fastening means such as a plurality of threaded bolts. Such wheels are commonly referred to as three-piece wheels.
Three-piece wheels generally comprise superimposed radially directed flanges extending from the inner and outer rims which are secured to a peripheral mounting on the wheel center by the fastening means. The advantage of a three-piece wheel is economy of repair. If one of the parts of the wheel is damaged, that part can be replaced without having to replace the entire wheel. However, inadequate strength and leakage are problems inherent in such structures. Inadequate strength results from the mechanical assembly and the tolerances required in the manufacture of such wheels which generally result in an imperfect alignment, adversely affecting wheel strength.
In addition to the obvious safety problems, inadequate strength has prevented such wheels from employing a desirable positive wheel offset which is highly advantageous, particularly for front drive vehicles, as it provides greater area for larger breaking drums for improved breaking performance while complying with existing wheel placement regulations. In an effect to solve these problems, numerous different three-piece wheel configurations have been developed. For example, U.S. Pat. No. 4,466,670 teaches a configuration which provides improved strength characteristics over previously developed three-piece wheels and employs a silicon seal to prevent leakage. U.S. Pat. No. 4,770,220 employs a rim design which provides sufficient strength to maximize the positive wheel offset. Nevertheless, regardless of the design, the necessity to manufacture and subsequently securement together the inner and outer rims in three-piece wheel designs necessarily increases the cost of manufacture and does not adequately address the problem of untrue alignment.
U.S. Pat. No. 4,693,104 provides a solution to the cost problem inherent in three-piece wheel construction by teaching a method of manufacturing a single piece aluminum alloy rim for use with conventional alloy wheel centers which reduces assembly time and the cost of manufacture while maximizing strength. However, the method disclosed therein requires the use of high pressure dies capable of exerting about 6,000 tons of pressure to form the wheel. While providing an excellent product and reducing the cost of manufacture as compared to three-piece wheels and correcting the problem of part alignment, the cost of the manufacturing equipment for such a process may be considered high for some manufacturers and the resultant two-piece wheel still requires an additional assembly step. It would therefore be highly desirable to develop a method of manufacturing an alloy wheel which would continue to provide a superior light weight product and true alignment, but which would further reduce the cost of manufacturing. The method of manufacture disclosed herein provides such a wheel.